There is a need for gas permeable materials having enhanced oleophobic and hydrophobic properties. Tetrafluoroethylene polymers are known to have hydrophobic properties and they are useful as hydrophobic films or as hydrophobic coatings on substrates. However, some tetrafluoroethylene polymers, such as polytetrafluoroethylene, are difficult to apply to substrates because they are not thermoplastic, and are not easily soluble. They cannot be applied by common thermoplastic extrusion techniques.
Gas air filters and vents have been made from porous material including porous polymers, such as porous polyolefins or polytetrafluoroethylene. However, even with porous polytetrafluoroethylene, the material has poor oleophobicity. This lack of resistance to oil penetration has impaired use of such materials as gaseous vents or filters in uses involving engines or devices that are commonly exposed to oil in the surrounding environment.